Traditionally production of glass bottles has been done on I-S machines by the blow and blow process. In this process, it is necessary to shape a parison and bottle neck ring with the parison in an inverted position, after which the parison is inverted to its normal position and placed in a finishing mold where it is blown to its final shape. The parisons are shaped in each of the sections of a plural (usually eight) section machine. A funnel is first connected to the parison mold to receive and guide a gob of molten glass so as to deliver it accurately to the parison mold. Following delivery of the gob, a baffle is connected over the funnel to supply a blow-down to insure that the gob settles to the bottom of the mold to fill the neck ring portion, correctly shape the neck ring and insure uniform contact of the glass with the walls of the parison mold. After the blow-down step, the baffle is disconnected and removed, the funnel is disconnected and removed and finally the baffle is again connected. With the funnel out of the way, the baffle functions as the bottom of the parison during the blow-back from the neck ring end which results in final shaping of the parison.
Any attempt to increase the rate of production of the machines may be broken down into a plurality of time periods as follows:
1. Time of shaping the neck ring
During this time, the funnel is connected to the parison mold, a gob of molten glass is dropped through the funnel into the mold, and the baffle is connected to the funnel to supply blow-down which assures filling of the neck ring mold and shaping of the neck ring.
2. Time of mechanical displacement
The gob of glass remains on the inside of the parison mold while the baffle is disconnected and withdrawn, the funnel is disconnected and withdrawn and the baffle is again connected.
3. Blow-back time
The parison is blown to conform it to the inside of the parison mold leaving the parison ready for inversion and deposit in the finishing mold for blowing to final shape.
With the present machines, a substantial number of bottles turn out to be defective due to nonuniform distribution of the glass in the walls of the bottles. The most frequent defect is known as a settle wave and consists of a thin ring of glass which extends around the blown bottle about three fourths of the way up from the bottles. It has been found that the quality of the bottles may be improved by increasing the blow-back time to insure a good inflation of the parison which results in more uniform distribution of glass in the walls of the bottle. However, in order to increase the blow-back time which previously was considered constant for any given type of bottle, the time for mechanical displacement had to be reduced. Reducing the time of mechanical displacement, however, appeared impossible due to the necessity of disconnecting and removing the baffle from the funnel, disconnecting and removing the funnel and then reconnecting the baffle directly onto the parison mold. Any attempt to speed up these movements of connecting and disconnecting were thought to be impossible because it would result in greater frictional losses between the parts. The conventional I-S machines also have the disadvantage that the baffle performs two functions in each shaping cycle, first by supplying a blow-down and then as a true baffle and any attempt to increase the speed of movements was thought to wear out the actuating mechanism more quickly.
U.S. Pat. No. 3,171,723 of 1965 represents one of the prior art attempts at reducing the length of the mechanical displacement time. In this patent, the upper part of the parison mold is shaped like a funnel in order to receive and guide the molten glass gob. However, instead of performing a blow-down in the upper part of the parison mold to insure good contact of the glass with the parison mold walls, a vacuum is created in the neck ring mold part followed by connecting the baffle to the bottom of the parison mold and performing the blow-back. Unfortunately, however, substituting a vacuum in the neck ring for the blow-down of the prior art did not result in uniform contact of the glass with the walls of the parison mold because there was a tendency for the glass to trap air bubbles between it and the parison mold walls which impedes uniform distribution of the glass.
Another prior art attempt to solve these problems may be found in U.S. Pat. No. 3,536,468 of 1970. In this patent, a unitary structure includes the parison molds and a funnel which are also connected with a mechanism for blow-down and spraying of lubricant onto the inside of the parison mold. In this way, the need to connect and disconnect the funnel is obviated and therefore, in a single operation the apparatus will guide, lubricate and perform blow-down. Such apparatus has the advantage that the funnel is connected with the mechanism for blow-down and spraying of lubricant and both are connected as a unit to the parison mold, so that only two operations are necessary, namely, to connect the baffle and perform blow-back. However, this apparatus suffers from being too heavy and bulky for fast movements and thus requires a movement time which is greater than in the standard machines. In addition, the design is somewhat complicated and has wear problems which make it relatively expensive to operate.
A similar showing may be found in U.S. Pat. No. 3,762,860 of 1972 with the difference that a lubricant spray nozzle is included which is shaped to fit a parison mold with a noncircular crosssection to premold the gob and produce parisons and bottles with a noncircular crosssection.